I doubt it is possible to actually see it, imagine you are living in underwater habitat, the habitat is not filled with air, it is filled with special blend of gases including helium and pressurized to greater than atmospheric pressure in order for divers to not have to undergo decompression after every dive. When you are inside this habitat, helium bubbles enter the watch, after the work is done, the habitat gets depressurized and the divers undergo decompression, during this phase the valve lets out helium bubbles....or if it would not have the valve, the crystal would pop off.